[PATCH 5.4 226/408] powerpc/tau: Check processor type before enabling TAU interrupt

Greg Kroah-Hartman
2020-10-27T14:40:45Z

From: Finn Thain <fthain@telegraphics.com.au>

[ Upstream commit 5e3119e15fed5b9a9a7e528665ff098a4a8dbdbc ]

According to Freescale's documentation, MPC74XX processors have an
erratum that prevents the TAU interrupt from working, so don't try to
use it when running on those processors.

Fixes: 1da177e4c3f41 ("Linux-2.6.12-rc2")
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Tested-by: Stan Johnson <userm57@yahoo.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/c281611544768e758bd58fe812cf702a5bd2d042.1599260540.git.fthain@telegraphics.com.au
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/powerpc/kernel/tau_6xx.c | 33 ++++++++++++++-------------------
arch/powerpc/platforms/Kconfig | 5 ++---
2 files changed, 16 insertions(+), 22 deletions(-)

diff --git a/arch/powerpc/kernel/tau_6xx.c b/arch/powerpc/kernel/tau_6xx.c
index b8d7e7d498e0a..614b5b272d9c6 100644
--- a/arch/powerpc/kernel/tau_6xx.c
+++ b/arch/powerpc/kernel/tau_6xx.c
@@ -40,6 +40,8 @@ static struct tau_temp
unsigned char grew;
} tau[NR_CPUS];

+static bool tau_int_enable;
+
#undef DEBUG

/* TODO: put these in a /proc interface, with some sanity checks, and maybe
@@ -54,22 +56,13 @@ static struct tau_temp

static void set_thresholds(unsigned long cpu)
{
-#ifdef CONFIG_TAU_INT
- /*
- * setup THRM1,
- * threshold, valid bit, enable interrupts, interrupt when below threshold
- */
- mtspr(SPRN_THRM1, THRM1_THRES(tau[cpu].low) | THRM1_V | THRM1_TIE | THRM1_TID);
+ u32 maybe_tie = tau_int_enable ? THRM1_TIE : 0;

- /* setup THRM2,
- * threshold, valid bit, enable interrupts, interrupt when above threshold
- */
- mtspr (SPRN_THRM2, THRM1_THRES(tau[cpu].high) | THRM1_V | THRM1_TIE);
-#else
- /* same thing but don't enable interrupts */
- mtspr(SPRN_THRM1, THRM1_THRES(tau[cpu].low) | THRM1_V | THRM1_TID);
- mtspr(SPRN_THRM2, THRM1_THRES(tau[cpu].high) | THRM1_V);
-#endif
+ /* setup THRM1, threshold, valid bit, interrupt when below threshold */
+ mtspr(SPRN_THRM1, THRM1_THRES(tau[cpu].low) | THRM1_V | maybe_tie | THRM1_TID);
+
+ /* setup THRM2, threshold, valid bit, interrupt when above threshold */
+ mtspr(SPRN_THRM2, THRM1_THRES(tau[cpu].high) | THRM1_V | maybe_tie);
}

static void TAUupdate(int cpu)
@@ -142,9 +135,8 @@ static void tau_timeout(void * info)
local_irq_save(flags);
cpu = smp_processor_id();

-#ifndef CONFIG_TAU_INT
- TAUupdate(cpu);
-#endif
+ if (!tau_int_enable)
+ TAUupdate(cpu);

size = tau[cpu].high - tau[cpu].low;
if (size > min_window && ! tau[cpu].grew) {
@@ -225,6 +217,9 @@ static int __init TAU_init(void)
return 1;
}

+ tau_int_enable = IS_ENABLED(CONFIG_TAU_INT) &&
+ !strcmp(cur_cpu_spec->platform, "ppc750");
+
tau_workq = alloc_workqueue("tau", WQ_UNBOUND, 1, 0);
if (!tau_workq)
return -ENOMEM;
@@ -234,7 +229,7 @@ static int __init TAU_init(void)
queue_work(tau_workq, &tau_work);

pr_info("Thermal assist unit using %s, shrink_timer: %d ms\n",
- IS_ENABLED(CONFIG_TAU_INT) ? "interrupts" : "workqueue", shrink_timer);
+ tau_int_enable ? "interrupts" : "workqueue", shrink_timer);
tau_initialized = 1;

return 0;
diff --git a/arch/powerpc/platforms/Kconfig b/arch/powerpc/platforms/Kconfig
index d82e3664ffdf8..92d7f2a7936e7 100644
--- a/arch/powerpc/platforms/Kconfig
+++ b/arch/powerpc/platforms/Kconfig
@@ -219,9 +219,8 @@ config TAU
temperature within 2-4 degrees Celsius. This option shows the current
on-die temperature in /proc/cpuinfo if the cpu supports it.

- Unfortunately, on some chip revisions, this sensor is very inaccurate
- and in many cases, does not work at all, so don't assume the cpu
- temp is actually what /proc/cpuinfo says it is.
+ Unfortunately, this sensor is very inaccurate when uncalibrated, so
+ don't assume the cpu temp is actually what /proc/cpuinfo says it is.

config TAU_INT
bool "Interrupt driven TAU driver (DANGEROUS)"
--
2.25.1